NIJMEGEN, NETHERLANDS. An elevated level of homocysteine is a risk factor for cardiovascular disease, stroke, and Alzheimer's disease and also increases the risk of a pregnant woman giving birth to a baby with neural tube defects. Supplementation with folic acid is known to lower homocysteine levels, but it is not known exactly how much is required and how long it takes to become effective. Researchers at the Nijmegen University Hospital have just completed a study aimed at answering these questions. The trial involved 144 healthy women (with normal homocysteine levels) between the ages of 18 and 40 years. The women were randomly allocated to one of three groups. Group 1 received 500 micrograms of folic acid daily for a four-week period, group 2 received 500 micrograms every second day (250 micrograms/day), and group 3 received a placebo. Blood samples were taken at the start of the trial and after one, two and four weeks when the supplementation phase ended. Samples were also taken four and eight weeks after the end of the supplementation to see how long its effect would last. Supplementation with both 500 micrograms/day and 500 micrograms every second day was found to be effective. Homocysteine levels decreased by an average 22 per cent in the women taking 500 micrograms/day and by 11 per cent in the ones taking 500 micrograms every second day. The level of folate in plasma and red blood cells also increased significantly. The homocysteine levels increased again when supplementation was stopped, but were still well below original levels eight weeks later. The major part of the drop in homocysteine level in the 500 micrograms/day group took place within the first two weeks. In view of the fact that neural tube defects develop in the third or fourth week of pregnancy it may be worthwhile to start taking folic acid immediately after missing the first period; although, of course, it would be better to start four weeks before a planned pregnancy. The magnitude of the observed drop in homocysteine concentration upon supplementation was found to be highly dependent on the initial level. Women with high levels (14.3 micromol/L) experienced a drop of around 4 micromol/L while women with lower initial levels only experienced drops of about 1 micromol/L.
Brouwer, Ingeborg A., et al. Low-dose folic acid supplementation decreases plasma homocysteine concentrations: a randomized trial. American Journal of Clinical Nutrition, Vol. 69, January 1999, pp. 99-104